Low density signature (LDS) is a code division multiple access (CDMA) technique in which spreading sequences for data symbols are sparse. Message passing algorithm (MPA) is a multi-user detection based on belief propagation (BP) for LDS modulation. MPA complexity is high such that it might not be feasible for implementation in practice for some cases, for example for modulations with higher orders or large number of multiplexed LDS signatures. However, MPA is a near optimal solution for LDS reception. LDS with MPA reception may provide good performance and features, but it may not be as practical as other solutions, such as orthogonal frequency-division multiple access (OFDMA). Reducing MPA complexity for detecting LDS modulation without substantially changing performance can improve MPA feasibility and usability for detecting LDS modulation, and makes MPA more suitable for cases with higher modulation orders or large number of multiplexed LDS signatures.